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Updated: May 5, 2025
In one instance, an old tendril, which had nearly ceased revolving, moved in one direction, whilst a young tendril above moved in an opposite course. The two uppermost internodes alone revolve; and as soon as the lower one grows old, only its upper part continues to move.
The thin upper internodes revolve, moving against the course of the sun, precisely like those of a true twiner, at an average rate, judging from three revolutions, of 3 hrs. 48 m.
It must be explained that the young plant of Oenothera has practically no stem, but a number of leaves radiating in all directions from the growing point which is near the surface of the soil. The plant is normally biennial, and in the first season the internodes are not developed.
Passiflora punctata. The internodes do not move, but the tendrils revolve regularly. A half-grown and very sensitive tendril made three revolutions, opposed to the course of the sun, in 3 hrs. 5 m., 2 hrs. 40 m. and 2 hrs. 50 m.; perhaps it might have travelled more quickly when nearly full-grown.
On the other hand, with most of the species of Bignonia and the Eccremocarpus, the internodes, tendrils, and petioles all revolved.
The free internodes of vigorously growing plants, when they cease to revolve, become straight, and show no tendency to be spiral; but when a shoot has nearly ceased to grow, or when the plant is unhealthy, the extremity does occasionally become spiral.
The movement is of the same nature as that of the revolving internodes, and, from the observations of Sachs and H. de Vries, no doubt is due to the same cause, namely, the rapid growth of a longitudinal band, which travels round the tendril and successively bows each part to the opposite side.
In the allied Eccremocarpus the internodes, petioles, and much- branched tendrils all spontaneously revolve together. The tendrils do not as a whole turn from the light; but their bluntly-hooked extremities arrange themselves neatly on any surface with which they come into contact, apparently so as to avoid the light.
New leaves would have come from the bud itself; in fact, the winter buds of the apple are packed with miniature leaves and sometimes with flowers as well. The shoot coming out of the bud may remain very short, constituting a "spur," or grow with long internodes, making a slender twig. The former, small and pointed, are leaf-buds; from them will arise a shoot bearing only leaves.
The young internodes sweep large circles, one being completed in 2 hrs. 15 m., and a second in 2 hrs. 55 m. By these combined movements of the internodes, petioles, and grapnel- like tendrils, the latter are soon brought into contact with surrounding objects. When a shoot stands near an upright stick, it twines regularly and spirally round it.
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